There is a need for a quick, easy and effective method for sealing leaking pipes, particularly underground pipes such as gas, water and sewer lines. This need is most acute in areas that have underground lines that were laid a number of years ago. Many of the leaks in the underground lines occur in the pipe joints due to deterioration of the original sealing materials. Further, the offending joints often have a plurality of minute leaks, making it diffcult to deduce the precise place repairs are needed. Also, it is particularly desirable to have a method of repair that enables the line to remain in service while it is being repaired so that there is a minimum amount of inconvenience to persons affected by the leaking line. Furthermore, a seal is needed that will provide an impervious barrier to prevent the escape of contents transported in the line, as well as the infiltration of contaminants from the surrounding environment.
The present invention is directed to solve these and concomitant problems. The disclosed invention teaches the use of a mixture of an exothermically reactive thermosettable acrylic adhesive, a blowing agent and a catalyst, for sealing leaks in pipes. One such use is disclosed in patent application Ser. No. 266,398 filed May 22, 1981, now U.S. Pat. No. 4,358,417, issued Nov. 9, 1982, and assigned to this Assignee, wherein the herein disclosed sealant was used to repair leaking bell and spigot joints.
In practicing this invention, it is essential that the sealant be used with a mold that completely surrounds and encases the leaking member and provides a cavity in the immediate vicinity of the leak which can be filled with the sealant. The sealant herein disclosed is primarily composed of elastomeric modified acrylic adhesive which is exothermically curable upon mixing with an appropriate catalyst. The other essential component of the sealant is a blowing agent which decomposes, releasing gaseous by-products during the exothermic reaction of the activated acrylic. In the absence of a catalyst, a mixture of the acrylic and blowing agent can be stored safely until needed. The catalyst is added to and mixed with the sealant and blowing agent immediately prior to insertion into the mold.
Once the acrylic has been activated, the temperature of the mixture begins to rise. It is essential, therefore, to transfer the activated mixture to the mold prior to appreciable reaction of the acrylic. When the appropriate temperature is reached, the blowing agent decomposes thus causing an increase in pressure within the mold. The pressure generated by the gaseous by-products produced by the decomposition of the blowing agent and by the rising temperature in the closed mold is greater than the pressure of the leaking gas or other material being transported through the pipe. Because of the internal pressure of the sealant mixture, the mixture expands and flows into the interstices of the pipe. Upon complete curing and solidification of the sealant, the sealant is bonded to the surface of the pipe. A filler or a plasticizer or both may be added to the acrylic-blowing agent mixture to increase the adhesive strength and the flexibility of the cured sealant. An odor mask may also be added.
The resulting seal is a dense highly cross-linked solid with numerous macroscopic isolated internal blowholes. The seal is impervious to moisture and is hihgly resistant to chemicals.
The disclosed invention offers many distinct advantages over the prior art. In repairing leaking underground pipes, such as gas lines and the like, it is necessary, to excavate the area surrounding the leaks. When using the disclosed invention, excavation can be kept to a minimum. Only an area sufficient to enable the leaking pipe to be cleaned and the mold to be placed around the leak need be dug. The sealant can be injected into the mold from ground level, thus eliminating the necessity of deep excavation and location shoring to enable someone to enter the excavation area. Furthermore, the only equipment needed to repair the leak, once the excavation has been made, is the mold and the container of sealant. With this invention, there is no need for an external source for applying heat, either prior to or after the injection of the mixture into the mold. Neither is there a need for an external source of pressure to force the sealant into the leaking interstices of the pipe.